Derivation
variable: pretomm2 [month of previous village stop] (table[s]: tb_tbxto2007, tbold_part1/2, tb_tboto2007, tbold_control)
variable: pretoyear2 [year of previous village stop] (table[s]: tb_tbxto2007, tbold_part1/2, tb_tboto2007, tbold_control)
recode pretomm2 0=1
recode pretoyear2 9999=. 0=.
gen pretodate2=mdy(pretomm2,15,pretoyear2) if pretomm2~=. & pretoyear2~=.
replace pretodate2=mdy(6,15,pretoyear2) if pretomm2==. & pretoyear2~=.